Reproductive biology

Male adenophoreans sometimes have thin cuticle extensions on both sides of the anus called bursae, which are fluid-filled body sacs. When present, bursae are used to hold females during copulation. Male testes, when present, are two in number and are shaped similar to the female ovary. The spicules, the male copulatory organ, are paired. Males have a single, ventral series of papilloid or tabloid pre-anal supplements. Sperm accumulate in the seminal vesicle and exit through the anus. During mating, the rigid spicules insert into the vagina and form a passageway for the sperm. The female ovary contains germ cells that produce eggs. Fertilization, mostly initiated by male sperm, takes place in the uterus, with eggs released through the vagina. (Most species produce males and females, but some species only produce hermaphrodites, in which both male and female structures are contained in the same individual.) Most eggs are about the same size and shape.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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